Fluorescence polarization-based assays hold tremendous promise for increasing throughput of drug screening programs. These assays detect when candidate drugs bind to target receptors, such as the dopamine, neurotensin, opioid, and serotonin receptors, which play key roles in the central nervous system. Compared to conventional radio-isotope assays, fluorescence assays are faster, simpler, and more versatile and safe. However, existing equipment for performing assays is in sufficient to meet the throughput needs in drug discovery programs. Pharmaceutical companies are looking for improvements in throughput and sensitivity. We propose to build on our knowledge of liquid crystal optics and imaging to develop a CCD-based microtitre plate reader that uses fluorescence polarization (FP) and that offers significant improvements in sensitivity and throughput compared to existing FP plate readers. Advances derive from a novel optical system, CCD-based simultaneous reading of all wells, and a novel background compensation scheme. Proposed Phase I work includes an analysis of sources of noise and error in FP measurements, microscope- based experiments to confirm model predictions, breadboard imaging experiments, and a preliminary optical design. The proposed system will work with any plate format (96, 384, or 1536 wells) and with multi-labeled samples exhibiting florescence intensity, resource energy transfer, and/or polarization. PROPOSED COMMERCIAL APPLICATION: Our plate reader would be used by drug discovery departments of pharmaceutical companies. The larger companies, of which there are at least 50, have between 20 and 50 drug screening programs going on at any given time. Most of the existing equipment is expected to be replaced by higher throughput instruments, when they become available. [unreadable]